Two basic arrangements have thus far been introduced for realizing the drive of embroidery tools of industrial embroidery machines.
According to one arrangement, a main motor with a main drive shaft is arranged along and across the embroidery machine. Cam plates for the individual drives of the embroidery tools are fastened on this main drive shaft. The movement is, via roller levers and additional transfer elements, transferred onto several oscillating shafts which extend along the entire machine and, in turn, actuate the linear movement of the corresponding embroidery tools at the numerous embroidery stations. A similar arrangement is described and schematically illustrated in FIG. 1 of DE 3,502,894.
According to a different arrangement, the main drive shaft is arranged along the machine. The corresponding cam plates are fastened on the front and the rear of this rotating main drive shaft. The movements are transferred from these cam plates onto different oscillating shafts which extend along the embroidery machine and, in turn, actuate the different embroidery tools at the numerous embroidery stations. Such an arrangement is illustrated in FIG. 1 of EP 0,193,625.
This particular patent also suggests a new solution in which the cam plates are replaced by highly dynamic electric motors, so that the different oscillating shafts which extend along the embroidery machine are driven by "electronic cam gears" in order to actuate the embroidery tools.
All three solutions have one severe disadvantage: when an industrial embroidery machine has a length of 10-20 m, it becomes very difficult to control the long oscillating shafts in a dynamic fashion at higher rotational speeds. The torsion and the torsional oscillations of these long shafts lead to a distortion of the movement to be performed by the embroidery tools as well as to a chronological phase displacement between the front and rear portion of the machine. This aspect represents one of the factors which limit the rotational speed of industrial embroidery machines if the machines operate with rotational speeds above 200 rpm.